1. Field of the Invention
The present invention relates to umbrellas and more particularly to an improved spring mechanism for large umbrella so as to provide an optimal expansible force while automatically opening the umbrella.
2. Description of Related Art
Conventionally, a large umbrella means an umbrella having a large canopy (i.e., large covering area). Accordingly, the thickness of canopy is increased, the frame is made large and its weight is increased. With this, the large umbrella may withstand a strong force exerted thereon by wind. But inevitably a user may have to exert a great force to open the large umbrella.
An improvement to above conventional large umbrella is to mount a spring between upper ring and lower ring. In a closed condition, spring is compressed to store an elastically energized force therein. When locking tab is deactivated, spring is automatically expanded to provide a main expansible force for opening the umbrella.
But this is still unsatisfactory for the purpose for which the invention is concerned for the following reasons:
1. The automatic opening mechanism is effected by a well chosen spring. However, there are many other factors (e.g., the joints between ribs and spreaders, the folded canopy sectors, or the like) consumed the elastic force of spring. As such, an ideal spring is not easy to find.
2. A spring with stronger elastic force than the optimum may exert an excessive upward force which may neutralize the elastic hub provided at the upper end of shank in a short period of time of use, thus shortening the useful life of umbrella. Also, the operation is labor consuming and much inconvenient.
3. A spring with weaker elastic force than the optimum may not exert a sufficient upward force to open the umbrella. As such, an additional manual force must be exerted to open the umbrella.
It is an object of the present invention to provide a spring mechanism for a large umbrella with automatic open feature wherein the spring mechanism is optimized such that a variety of advantages such as smooth operation; less labor consuming, reliable, and prolonged useful time are obtained.
To achieve the above and other objects, the present invention provides an auxiliary elastic support mechanism for a large umbrella with automatic open feature, the umbrella being supported by a plurality of ribs and a plurality of spreaders, the mechanism comprising a plurality of hollow cylindrical rib joint members each put on the rib having a pivot joint and a first spring anchoring lug; a plurality of hollow cylindrical spreader joint members, each having an outer end secured to one of the rib joint members, an inner end for receiving the spreader therein, and a second spring anchoring lug; and a plurality of auxiliary springs each having an outer hook engaged with the first spring anchoring lug and an inner hook engaged with the second spring anchoring lug.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.